Monday, November 30, 2009

Inspired by phase transitions displayed in condensed matter physics, Petr Hořava has constructed a model where the time dimension is decoupled from space at high energy/short distance while the space-time characteristic of relativity (and Lorentz invariance) emerges at low energy/long distances. The model, which is a quantum field theory, is able to be renormalized in a way GR itself cannot be. The paper, “Quantum Gravity at a Lifshitz Point,” sets out the theory.

Friday, November 20, 2009

The universe, or cosmos, consists of a four-dimensional space-time continuum which contains matter and energy. It all began with a big bang singularity: time as well as space started then, so it doesn’t make sense to ask what happened “before”. The universe probably extends beyond what is observable, but the same physical laws prevail everywhere. Nothing exists outside the universe.

Tuesday, November 10, 2009

I’ve never studied Spinoza in any depth, so have been ignorant of the many subtleties/ambiguities in his work and the competing interpretations put forward by scholars on many points. I enjoyed reading two articles by Samuel Newlands: first, his SEP article “Spinoza’s Modal Metaphysics”, and the recent preprint, “Another Kind of Spinozistic Monism.” The latter paper argues that the various forms of metaphysical dependence employed by Spinoza (causation, inherence in, following from, etc.) are each connected to a broad notion of conceptual dependence, which is the key to understanding their role. This paper, interesting in its own right, helped me understand Newlands’ work in the modal metaphysics article, which is directly about the aspect of Spinoza I’m most interested in at the moment.

Spinoza is widely seen as a necessitarian (everything which exists does so necessarily), and for good reason: he has passages which explicitly affirm this. But evidently if you dig deeper there is a subtlety with regard to the status of “finite modes”, the ontological category which would include everyday concrete things. (Please note the use of “modes” here is unrelated to the “modal” dimensions of necessity and contingency). The one substance (God) and its infinite modes are absolutely necessary, but finite modes don’t follow from God in the same way as infinite modes. On the one hand, Spinoza affirms that God created everything, but elsewhere he specifies that finite modes follow only from other finite modes. What does this mean for the modal status of finite things (and how can he affirm both of these statements?)